Over the last years, a concept known as the Internet of Things (IoT) has emerged. Generally, IoT comprises a huge number of small autonomous devices, which typically, more or less infrequently (e.g. once per week to once per minute) transmit and receive only small amounts of data, or are polled for data. These devices are sometimes referred to as Machine Type Communication (MTC) devices, Machine-to-Machine (M2M) devices or just Machine Devices (MDs), and are assumed not to be associated with humans, but are rather sensors or actuators of different kinds, which typically communicate with application servers (which configure and receive data from the devices) within or outside the cellular network.
With the nature of MTC devices and their assumed typical uses follow that these devices generally will have to be energy efficient, since external power supplies not necessarily are available and since it is neither practically nor economically feasible to frequently replace or recharge their batteries. In some scenarios the MTC devices may not even be battery powered, but may instead rely on energy harvesting, i.e. gathering energy from the environment, opportunistically utilizing (the often very limited) energy that may be tapped from sun light, temperature gradients, vibrations, etc. Sleep cycles are commonly used for the MTC device in order to conserve power.
So far, the MTC related work in 3rd Generation Partnership Project (3GPP) has focused on MTC devices directly connected to the cellular network via the radio interface of the cellular network. However, a scenario which is likely to be more prevalent is that most MTC devices connect to the cellular network via a gateway. In such scenarios the gateway acts like a User Equipment (UE) towards the cellular network while maintaining a local network, typically based on a short range radio technology towards the MTC devices. Such a local network, which in a sense extends the reach of the cellular network (to other radio technologies but not necessarily in terms of radio coverage) has been coined capillary network and the gateway connecting the capillary network to the cellular network is thus referred to as a capillary network gateway (CGW). Hence, the capillary network comprises one or more CGWs and a plurality of MTC devices, which connect to a Radio Access Network (RAN) of an available cellular communications network via the one or more CGWs.
Radio technologies that are expected to be common in capillary networks include e.g. IEEE 802.15.4 (e.g. with IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) or ZigBee as higher layers), Bluetooth Low Energy or low energy versions of the IEEE 802.11 family (i.e. Wi-Fi). Generally, the CGW is under the control of the operator of the cellular network (even though the cellular network operator not necessarily owns the CGW). There are multiple protocols that can be used for managing the devices in a capillary network, such as Simple Network Management Protocol (SNMP) and Open Mobile Alliance (OMA) Lightweight Implementation (LWM2M). In these structures, multiple MTC devices are controlled by a number of managers, where the managers typically communicate with an agent running at the respective MTC device.
Sending commands to the MTC devices from the managers requires the MTC device to listen, either actively (i.e. the device “pulls” the commands from the manager) or passively (i.e. the manager “pushes” the commands onto the device), for the incoming commands. Regardless of if push or pull transfer is utilized, the MTC devices will inevitably consume power to acquire the commands and carry out instructions accordingly. Further, some MTC devices may have multiple managers (e.g. a sensor which reports temperature may be polled for the latest reading by multiple users via multiple managers), which can lead to excessive signalling with the device, some of which might be duplicate or contradictory commands. This results in inefficient use of the limited resources of the MTC device.